In recent years, there have been reported a large number of organic synthesis reactions using transition metal catalysts obtained by coordinating tertiary phosphine with a sterically bulky hydrocarbon group such as a tert-butyl group or an adamantyl group to transition metals such-as palladium (see, for example, “Journal of the American Chemical Society” (U.S.A.), 1999, vol. 121, pp. 4369-4378, “Journal of the Organic Chemistry” (U.S.A.), 2000, vol. 65, pp. 1158-1174).
As a process for synthesizing tertiary phosphine compounds with, as an attached bulky hydrocarbon group, an attached tert-butyl group, a process comprising reacting di-tert-butylphosphinous chloride with a lithium reagent of alkyl or aryl or a Grignard reagent of alkyl or aryl has been heretofore known, as shown in the following examples (1) to (9).
Especially when a tertiary alkyl group is introduced into di-tert-butylphosphinous chloride, only an alkyllithium reagent is employed as shown in the process described in the following document (1), because an alkyl Grignard reagent suffers large steric hindrance and therefore has low reactivity.
(1) In “Chemische Berichte” (Germany), 1967, vol. 100, p. 693, it is described that tri-tert-butylphosphine is obtained in a yield of 50% by a process comprising reacting di-tert-butylphosphinous chloride with tert-butyllithium in a benzene-pentane mixed solvent.
In this process, however, tert-butyllithium that is tertialy alkyllithium is used as a starting material, and in the preparation process and the handling thereof, there are problems such as the following problems (i) and (ii), so that this process cannot be said to be convenient as an industrial production process.
(i) For preparing tertiary alkyllithium, a highly active lithium fine dispersion must be formed at a high temperature (about 200° C.), and the fine dispersion must be reacted with a tertiary alkyl halide using a low-boiling hydrocarbon as a solvent in a stream of argon. Therefore, reaction in a special vessel is required, and sufficient attention is necessary for the reaction operation.
(ii) The tertiary alkyllithium thus formed is a highly dangerous reagent which undergoes spontaneous ignition when it comes into contact with air.
(2) In “Journal of the Chemical Society (C)” (United Kingdom), 1971, p. 1931, it is described that di-tert-butylphenylphosphine is obtained in a yield of 60% by a process comprising reacting di-tert-butylphosphinous chloride with a phenyllithium reagent in an ether solvent.
In this process, however, metallic lithium that is dangerous in handling or alkyllithium that is expensive must be used in order to synthesize an aryllithium reagent that is a starting material. In the industrial production, therefore, there are problems in respects of safety and cost.
(3) In the pamphlet of International Publication No. 99/9040, pp. 5-6, it is described that α,α′-bis(di-tert-butylphosphino)-o-xylene is obtained in a yield of 61.8% by a process comprising reacting a Grignard reagent, which has been prepared from α,α′-dichloro-o-xylene and magnesium in a tetrahydrofuran solvent, with di-tert-butylphosphinous chloride of 4 equivalents at 50° C. for 24 hours.
In this process, di-tert-butylphosphinous chloride in an amount of 4 equivalents to the Grignard reagent that is a starting material is necessary, but the yield of the aimed product is low, and in the industrial production, this process is disadvantageous in respect of cost.
(4) In “Chemische Berichte” (Germany), 1967, vol. 100, p. 693, it is described that di-tert-butylisopropylphosphine is obtained by a process comprising reacting a Grignard reagent, which has been prepared from isopropyl bromide and magnesium, with di-tert-butylphohsphinous chloride.
In this process, the reaction is not completed, and the aimed product is obtained only as a mixture with di-tert-butylphosphinous chloride that is a starting material.
(5) In “Bulletin of the Korean Chemical Society” (Korea), 1999, vol. 20, p. 601, it is described that 1-(di-tert-butylphosphinomethyl)-o-carborane is obtained in a yield of 39% by a process comprising reacting a Grignard reagent, which has been prepared from 1-(bromomethyl)-o-carborane and magnesium, with di-tert-butylphosphinous chloride in ether for 2 hours under reflux.
In this process, the aimed product is obtained only in a low yield.
(6) In “Journal of the American Chemical Society” (U.S.A.), 1999, vol. 121, p. 4373, it is described that 2-(di-tert-butylphosphino)biphenyl is obtained in a yield of 67% by a process comprising reacting a Grignard reagent, which has been prepared from 2-bromobiphenyl and magnesium in tetrahydrofuran, with copper(I) chloride of 1.05 mol times the amount of 2-bromobiphenyl and with di-tert-butylphosphinous chloride of 1.20 mol times the amount of 2-bromobiphenyl for 8 hours under reflux, adding hexane and ether at room temperature, then temporarily taking out a copper complex of the aimed product as a solid and treating the copper complex with a mixture solution of hexane, ethyl acetate and an ammonia aqueous solution.
In this process, copper(I) chloride of 1.05 mol times the amount of 2-bromophenyl is used, and after the reaction, the aimed product is temporarily taken out of the system as a solid copper complex, and in order to decompose the copper complex, the copper complex is treated with ammonia water that is highly poisonous and causes environmental pollution. In this process, therefore, the reaction operations are complicated, and there is a problem in respect of working safety. In addition, a large amount of waste liquor containing copper and ammonia is produced, so that this process is not favorable as an industrial production process.
(7) In U.S. Pat. No. 6,307,087, it is described in the working examples that di-tert-butylphosphinous chloride is reacted with an aryl Grignard reagent using copper(I) chloride in an amount almost equimolar with di-tert-butylphosphinous chloride, more specifically, 2-(di-tert-butylphosphino)-4′-trifluoromethyl-biphenyl is obtained in a yield of 31% by a process comprising adding di-tert-butylphosphinous chloride and copper(I) chloride of 0.91 mol time the amount of di-tert-butylphosphinous chloride to a Grignard reagent, which has been prepared from 2-bromo-4′-trifluoromethyl-biphenyl and magnesium, reacting them for 14 hours with heating, then filtering a suspension obtained by diluting the reaction mixture with ether, and treating the resulting solid with ethyl acetate and ammonia water.
In this process, the aimed product is obtained only in a low yield. Further, copper(I) chloride is used in an amount almost equimolar with di-tert-butylphosphinous chloride, and in order to liberate the aimed product from the copper complex, treatment with ammonia water is essential. Therefore, there are problems similar to those in the document (6).
(8) In “Advanced Synthesis & Catalysis” (Germany), 2001, No. 8, p. 793, it is described that 2-(di-tert-butylphosphino)-2′-dimethylamino-biphenyl is obtained in a yield of 47% by a process comprising adding copper(I) chloride (15% by mol based on di-tert-butylphosphinous chloride) to a Grignard reagent, which has been prepared from 2-bromo-N,N-dimethylaniline, 2-bromochlorobenzene and magnesium, mixing them, subsequently adding di-tert-butylphosphinous chloride, reacting them at 60° C. for 20 hours, then adding an organic solvent and ammonia water and filtering the resulting reaction solution through Celite.
In this process, the amount of the copper compound used is decreased as compared with that in the document (6), and post treatment is carried out without taking out a copper complex of the aimed product from the reaction solution, but the yield is low. In addition, a problem of use of ammonia water has not been solved.
(9) In the pamphlet of International Publication No. 02/48160, p 17, it is described that di-tert-butyl(1-adamantyl)phosphine is obtained in a yield of 86% by a process comprising adding a 1-adamantylmagnesium bromide solution to a solution obtained by adding di-tert-butylphosphinous chloride, copper(I) iodide of 10% by mol and lithium bromide of 20% by mol based on the di-tert-butylphosphinous chloride to a solvent, reacting them at room temperature for 17 hours and filtering a solution obtained by solvent replacement of the reaction solution with benzene, through Celite.
In this process, the Grignard reagent is used in an amount of 2 mol times the amount of the di-tert-butylphosphinous chloride. Moreover, lithium bromide is used in addition to the copper compound, and after the reaction, it is necessary to perform solvent replacement with benzene that is carcinogenic and to perform filtration using Celite. Hence, there are problems in respects of economical efficiency, safety and workability.
Accordingly, any of the above processes is not industrially satisfactory.
Under such circumstances, development of a process for producing tertiary phosphine with an attached bulky hydrocarbon group such as a tert-butyl group or an adamantyl group in a high yield and with high purity on an industrial scale through simple and safe operations has been expected.
The present inventors have earnestly studied to solve the above problems, and as a result, they have found that tertiary phosphine can be produced in a high yield and with high purity by allowing a dialkylphosphinous halide having a tertiary hydrocarbon group to react with a Grignard reagent in the presence of a specific amount of a copper compound. Based on the finding, the present invention has been accomplished.
It is an object of the present invention to produce tertiary phopsphine with an attached sterically bulky hydrocarbon group, which is useful as a ligand of a transition metal catalyst in organic synthesis reactions, in a high yield and with high purity on an industrial scale through simple and safe operations.